Medical devices including ablation electrodes

ABSTRACT

Medical devices and methods for making and using medical devices are disclosed. An example medical device may be a renal nerve modulation catheter. The catheter may include an elongate catheter shaft. The catheter shaft may have a plurality of cuts formed therein define a plurality of electrode assemblies. The electrode assemblies may each include a main strut, one or more branched spacer struts extending from the main strut, and an electrode extending from the main strut and positioned radially inward from the spacer struts.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to U.S. Provisional Application Ser. No. 61/545,419, filed Oct. 10, 2011, the entirety of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure pertains to medical devices, and methods for manufacturing medical devices. More particularly, the present disclosure pertains to renal nerve modulation and/or ablation medical devices and methods for manufacturing and using such devices.

BACKGROUND

A wide variety of intracorporeal medical devices have been developed for medical use, for example, intravascular use. Some of these devices include guidewires, catheters, and the like. These devices are manufactured by any one of a variety of different manufacturing methods and may be used according to any one of a variety of methods. Of the known medical devices and methods, each has certain advantages and disadvantages. There is an ongoing need to provide alternative medical devices as well as alternative methods for manufacturing and using medical devices.

BRIEF SUMMARY

The invention provides design, material, manufacturing method, and use alternatives for medical devices. An example medical device may be a renal nerve modulation catheter. The catheter may include an elongate catheter shaft. The catheter shaft may have a plurality of cuts formed therein that define a plurality of electrode assemblies. The electrode assemblies may each include a main strut, one or more branched spacer struts extending from the main strut, and an electrode extending from the main strut and positioned radially inward from the spacer struts.

An example method for manufacturing a renal nerve modulation catheter may include providing a tubular member and laser cutting the tubular member. Laser cutting the tubular member may define a plurality of electrode assemblies in the tubular member. The electrode assemblies may each include a main strut, one or more branched spacer struts extending from the main strut, and an electrode extending from the main strut and positioned radially inward from the spacer struts.

Another example renal nerve modulation catheter may include an elongate tubular member having an electrode array portion. The electrode array portion may have a plurality of cuts formed therein that define a plurality of longitudinally-spaced electrode assemblies. The electrode assemblies each include a main strut, one or more branched spacer struts extending from the main strut, and an electrode extending from the main strut and positioned radially inward from the spacer struts.

The above summary of some embodiments is not intended to describe each disclosed embodiment or every implementation of the present invention. The Figures, and Detailed Description, which follow, more particularly exemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:

FIG. 1 is a schematic view illustrating an example renal nerve modulation system;

FIG. 2 is a schematic view illustrating the location of the renal nerves relative to the renal artery;

FIG. 3 is a side view of a portion of an example catheter with the catheter shaft cut and laid flat;

FIG. 4 is a perspective view of a portion of an example electrode assembly;

FIG. 5 is a partial cross-sectional side view of an example catheter disposed within a body lumen; and

FIG. 6 is a perspective view of a portion of another example electrode assembly.

While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

DETAILED DESCRIPTION

For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification.

All numeric values are herein assumed to be modified by the term “about,” whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the terms “about” may include numbers that are rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention.

It is noted that references in the specification to “an embodiment”, “some embodiments”, “other embodiments”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with one embodiment, it should be understood that such feature, structure, or characteristic may also be used connection with other embodiments whether or not explicitly described unless cleared stated to the contrary.

Certain treatments may require the temporary or permanent interruption or modification of select nerve function. One example treatment is renal nerve ablation which is sometimes used to treat conditions related to congestive heart failure. The kidneys produce a sympathetic response to congestive heart failure, which, among other effects, increases the undesired retention of water and/or sodium. Ablating some of the nerves running to the kidneys may reduce or eliminate this sympathetic function, which may provide a corresponding reduction in the associated undesired symptoms.

Many nerves (and nervous tissue such as brain tissue), including renal nerves, run along the walls of or in close proximity to blood vessels and thus can be accessed intravascularly through the walls of the blood vessels. In some instances, it may be desirable to ablate perivascular nerves using a radio frequency (RF) electrode. In other instances, the perivascular nerves may be ablated by other means including application of thermal, ultrasonic, laser, microwave, and other related energy sources to the vessel wall.

Because the nerves are hard to visualize, treatment methods employing such energy sources have tended to apply the energy as a generally circumferential ring to ensure that the nerves are modulated. However, such a treatment may result in thermal injury to the vessel wall near the electrode and other undesirable side effects such as, but not limited to, blood damage, clotting, weakened vessel wall, and/or protein fouling of the electrode.

While the devices and methods described herein are discussed relative to renal nerve modulation through a blood vessel wall, it is contemplated that the devices and methods may be used in other applications where nerve modulation and/or ablation are desired. The term modulation refers to ablation and other techniques that may alter the function of affected nerves.

FIG. 1 is a schematic view of an example renal nerve modulation system 10 in situ. System 10 may include a renal modulation catheter 12 and one or more conductive element(s) 14 for providing power to catheter 12. A proximal end of conductive element(s) 14 may be connected to a control and power element 16, which supplies necessary electrical energy to activate one or more electrodes (e.g., electrode 24 as shown in FIG. 3) disposed at or near a distal end of catheter 12. When suitably activated, the electrodes are capable of ablating adjacent tissue. The terms electrode and electrodes may be considered to be equivalent to elements capable of ablating adjacent tissue in the disclosure which follows. In some instances, return electrode patches 18 may be supplied on the legs or at another conventional location on the patient's body to complete the circuit. Control and power element 16 may include monitoring elements to monitor parameters such as power, temperature, voltage, pulse size and/or shape and other suitable parameters, with sensors mounted along catheter, as well as suitable controls for performing the desired procedure. In some embodiments, power element 16 may control a radio frequency (RF) electrode. The electrode may be configured to operate at a frequency of approximately 460 kHz. It is contemplated that any desired frequency in the RF range (e.g., about 3 kHz to 300 GHz) may be used, for example, from about 100-1000 kHz, or from about 400-600 kHz, or from 450-500 kHz. These are just examples. It is further contemplated that additionally and/or other ablation devices may be used as desired, for example, but not limited to resistance heating, ultrasound, microwave, and laser devices and these devices may require that power be supplied by the power element 18 in a different form.

FIG. 2 illustrates a portion of the renal anatomy in greater detail. More specifically, the renal anatomy includes renal nerves RN extending longitudinally along the lengthwise dimension of renal artery RA and generally within the adventitia of the artery. As will be seen in the figure, the circumferential location of the nerves at any particular axial location may not be readily predicted. Nerves RA are difficult to visualize in situ and so treatment methods may desirably rely upon ablating multiple sites to ensure nerve modulation.

FIG. 3 is a cut away side view of catheter 12. Here, some of the structural features of catheter 12 can be seen. For example, catheter 12 may include a catheter shaft 20. In FIG. 3, catheter shaft 20 is axially cut and laid flat for illustration purposes. Catheter shaft 20 may take the form of a metallic and/or polymer shaft and may include visualization (e.g., marker bands), orientation markings, and/or reinforcing structures (e.g., braids, coils, etc.) commonly used for catheter shafts. In at least some embodiments, catheter shaft 20 may form or define an outer surface of catheter 12. In other embodiments, an outer shaft 25 may be disposed about catheter shaft 20 as depicted schematically in FIG. 3. Similar structural features may also be incorporated in outer shaft 25 (e.g., visualization, orientation markings, reinforcements, etc.).

Catheter shaft 20 may include a first region 21, a second region 22, and an electrode or ablation region 23. In some embodiments, first region 21 may be a proximal region and second region 22 is a distal region. The reverse may also be true. First region 21, second region 22, or both may have a plurality of slots 38 formed therein. Slots 38 may provide regions 21/22 with increased flexibility. Alternatively, portions or all of regions 21/22 may be uncut or have any other suitable configuration. In some embodiments, ablation region 23 is continuous with or otherwise unitary with regions 21/22. Alternatively, ablation region 23 may be a distinct tube that is attached to regions 21/22.

Ablation region 23 may be or otherwise include a tube that is cut so as to define one or more electrodes therein. For example, ablation region 23 may include a first electrode 24 a that includes a first main strut 26 a coupled thereto. Another strut region 26 a′ may also be coupled to electrode 24 a, which may ultimately form spacer struts 28/30 and strut regions 32/34 as shown in FIG. 4 and discussed below. Ablation region 23 may also include additional electrodes (and struts) including a second electrode 24 b having a second main strut 26 b and a second strut region 26 b′, a third electrode 24 c having a third main strut 26 c and a third strut region 26 c′, a fourth electrode 24 d having a fourth main strut 26 d and a fourth strut region 26 d′, and a fifth electrode 24 e having a fifth main strut 26 e and a fifth strut region 26 e′. Each electrode/strut may be associated with a conductive trace such as conductive traces 27 a/27 b/27 c/27 d/27 e. In at least some embodiments, conductive traces 27 a/27 b/27 c/27 d/27 e may be electrically coupled with the corresponding electrode 24 a/24 b/24 c/24 d/24 e, trace or otherwise follow struts 26 a/26 b/26 c/26 d/26 e, and trace or otherwise follow catheter shaft 20 to a position where they are coupled to conductive element 14 and/or control and power element 16. Alternatively, conductor wire(s) may be used in place of conductive traces 27 a/27 b/27 c/27 d/27 e. In these embodiments, solder, conductive adhesive, or crimp attachments may be used to attached the wires to electrodes 24 a/24 b/24 c/24 d/24 e. The wires may be disposed at essentially any suitable location such as along the interior or lumen of catheter shaft 20, along exterior regions of catheter shaft 20, etc. In some embodiments, a polymer tube may be coextruded onto the wires or along portions of the wires.

In general, ablation region 23 may be designed so that a relatively complex array of electrodes (and/or “electrode assemblies”, which for the purposes of this disclosure may be understood to be the combination of an individual electrode and the corresponding struts) can be formed in a relatively simple manner (e.g., cutting a portion of catheter shaft 20 so as to define a plurality of electrodes). In addition, the construction of the array from catheter shaft 20 may allow the overall profile of catheter 12 to be kept as small as possible, if desired. Furthermore, laser cutting procedures have become sufficiently sophisticated so that a variety of designs can be produced and/or tailored to the needs of a particular intervention. The number of electrodes, shape of electrodes and/or struts, and the overall form of ablation region 23 may vary. For example, ablation region 23 may include one, two, three, four, five, six, seven, eight, nine, ten, or more electrodes. The electrodes may be arranged so as to form a circumferentially and axially spaced array of electrodes (e.g., as depicted in FIG. 3). However, other embodiments are contemplated where one or more electrodes may be disposed at the same axial location and/or have a different circumferential spacing/arrangement. In addition, electrodes 24 a/24 b/24 c/24 d/24 e and struts 26 a/26 b/26 c/26 d/26 e are shown in FIG. 3 as being relatively straight and with straight lines. Alternative embodiments are contemplated including those with a curved or rounded configuration.

Each of electrodes 24 a/24 b/24 c/24 d/24 e may generally take the form of or otherwise includes a conductive region that functions as the electrode. Conductive traces 27 a/27 b/27 c/27 d/27 e may be coupled thereto (and, ultimately, to control and power element 16) so as to supply the appropriate energy to electrodes 24 a/24 b/24 c/24 d/24 e. For example, conductive traces 27 a/27 b/27 c/27 d/27 e may extend to and connect with electrodes 24 a/24 b/24 c/24 d/24 e. In at least some embodiments, conductive traces 27 a/27 b/27 c/27 d/27 e are independently attached to the corresponding electrode 24 a/24 b/24 c/24 d/24 e so that each individual electrode 24 a/24 b/24 c/24 d/24 e can be energized independently of one another. An insulation layer may be applied to, for example, the edges of electrodes 24 a/24 b/24 c/24 d/24 e (e.g., which may reduce current concentrations at the edges), the outer surface of catheter shaft 20, an outer surface of struts 26 a/26 b/26 c/26 d/26 e, along conductive traces 27 a/27 b/27 c/27 d/27 e, or along any other suitable portion of catheter 12. The insulation layer(s) may be applied by any suitable technique such as, for example, a chemical technique, a vapor technique, sputtering, masking, spraying, printing, or the like. Ancillary methods such as laser or other directed beam or field processes may be used to attract the insulation materials, to adhere the materials, or to remove materials. In addition, other structures may also be added to catheter shaft 20 that may assist or aid the functioning of catheter 12 such as thermocouples, thermistors, etc.

In at least some embodiments, catheter shaft 20 is configured to shift between a first generally collapsed configuration and a second generally expanded configuration. Catheter shaft 20 can be held in the collapsed configuration by outer shaft 25 as depicted schematically in FIG. 3. It can be appreciated that in practice, outer shaft 25 may be disposed along the exterior surface of catheter shaft 20 in order to efficiently hold catheter shaft 20 in the collapsed configuration. In at least some embodiments, catheter shaft 20 is formed from or otherwise includes a self-expanding material so that shifting catheter shaft 20 from the collapsed configuration to the expanded configuration may occur by retracting outer shaft 25. FIG. 4 illustrates a portion of catheter shaft 20 in the expanded configuration. Here, electrode 24 a and main strut 26 a are shown, which together form an electrode assembly 40. Main strut 26 a may branch, forming a pair of spacer struts 28/30. In at least some embodiments, spacer struts 28/30 are disposed radially outward relative to main strut 26 a when catheter shaft 20 is in the expanded configuration. In addition, main strut 26 a also may lead to electrode 24 a and flanking strut regions 32/34 that flank electrode 24 a. Strut regions 32/34 are disposed radially inward relative to spacer struts 28/30. Strut regions 32/34 may also be disposed radially inward relative to main strut 26 a. Other arrangements are contemplated where a differing number of spacer struts 28/30 are utilized (fewer or more), a different arrangement or shape is utilized for spacer struts 28/30 and/or strut region 32/34, or other structural arrangements are utilized.

In general, the arrangement of spacer struts 28/30 and strut regions 32/34 may help to space electrode 24 a from the wall of blood vessel 36 as illustrated in FIG. 5. This may be desirable for a number of reasons. For example, spacing electrode 24 a from the wall of blood vessel 36 may allow for increased heat transfer and/or dissipation to occur. Also seen in FIG. 5 are electrodes 24 b/24 c/24 d/24 e. Here the circumferential spacing and/or arrangement of electrodes 24 a/24 b/24 c/24 d/24 e can be seen. Axial spacing is also contemplated, although not spatially represented in the drawing.

One example manufacturing process contemplated for catheter 12 can include cutting catheter shaft 20, heat setting the expanded configuration of catheter shaft 20, coating an insulation layer on catheter shaft 20, masking and/or selectively removing a portion of the insulation layer, and applying conductive traces (and/or coupling electrode wires 27 a/27 b/27 c/27 d/27 e with electrodes 24 a/24 b/24 c/24 d/24 e). This is just an example. This process may represent a relatively simply overall process with relatively few manufacturing steps. Such a process would help to reduce overall manufacturing costs and/or resources required.

FIG. 6 illustrates another example electrode assembly 124 that may be used with any of the catheters and/or catheter shafts disclosed herein. Electrode assembly 124 may include main strut 126 that branches into spacer struts 128/130. In addition, electrode assembly 124 may include an electrode region 140 flanked by strut regions 132/134. A temperature monitoring member 142 (e.g., a thermocouple, an insulated thermocouple junction, a thermistor, or the like) may be disposed along region 140. Conductive trace 127 may be coupled to temperature monitoring member 142. While not shown explicitly connected to electrode region 140, another conductive trace 144 may be coupled to electrode region 140. Trace 127 and/or trace 144 may include an insulation layer or coating.

The materials that can be used for the various components of catheter 12 (and/or other catheters disclosed herein) and the various bodies and/or members disclosed herein may include those commonly associated with medical devices. For simplicity purposes, the following discussion makes reference to catheter shaft 20 and other components of catheter 12. However, this is not intended to limit the devices and methods described herein, as the discussion may be applied to other similar tubular members and/or components of tubular members or devices disclosed herein.

Catheter shaft 20 and/or other components of catheter 12 may be made from a metal, metal alloy, polymer (some examples of which are disclosed below), a metal-polymer composite, ceramics, combinations thereof, and the like, or other suitable material. Some examples of suitable metals and metal alloys include stainless steel, such as 304V, 304L, and 316LV stainless steel; mild steel; nickel-titanium alloy such as linear-elastic and/or super-elastic nitinol; other nickel alloys such as nickel-chromium-molybdenum alloys (e.g., UNS: N06625 such as INCONEL® 625, UNS: N06022 such as HASTELLOY® C-22®, UNS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys, and the like), nickel-copper alloys (e.g., UNS: N04400 such as MONEL® 400, NICKELVAC® 400, NICORROS® 400, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such as MP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 such as HASTELLOY® ALLOY B2®), other nickel-chromium alloys, other nickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-iron alloys, other nickel-copper alloys, other nickel-tungsten or tungsten alloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like); platinum enriched stainless steel; titanium; combinations thereof; and the like; or any other suitable material.

As alluded to herein, within the family of commercially available nickel-titanium or nitinol alloys, is a category designated “linear elastic” or “non-super-elastic” which, although may be similar in chemistry to conventional shape memory and super elastic varieties, may exhibit distinct and useful mechanical properties. Linear elastic and/or non-super-elastic nitinol may be distinguished from super elastic nitinol in that the linear elastic and/or non-super-elastic nitinol does not display a substantial “superelastic plateau” or “flag region” in its stress/strain curve like super elastic nitinol does. Instead, in the linear elastic and/or non-super-elastic nitinol, as recoverable strain increases, the stress continues to increase in a substantially linear, or a somewhat, but not necessarily entirely linear relationship until plastic deformation begins or at least in a relationship that is more linear that the super elastic plateau and/or flag region that may be seen with super elastic nitinol. Thus, for the purposes of this disclosure linear elastic and/or non-super-elastic nitinol may also be termed “substantially” linear elastic and/or non-super-elastic nitinol.

In some cases, linear elastic and/or non-super-elastic nitinol may also be distinguishable from super elastic nitinol in that linear elastic and/or non-super-elastic nitinol may accept up to about 2-5% strain while remaining substantially elastic (e.g., before plastically deforming) whereas super elastic nitinol may accept up to about 8% strain before plastically deforming. Both of these materials can be distinguished from other linear elastic materials such as stainless steel (that can also can be distinguished based on its composition), which may accept only about 0.2 to 0.44 percent strain before plastically deforming.

In some embodiments, the linear elastic and/or non-super-elastic nickel-titanium alloy is an alloy that does not show any martensite/austenite phase changes that are detectable by differential scanning calorimetry (DSC) and dynamic metal thermal analysis (DMTA) analysis over a large temperature range. For example, in some embodiments, there may be no martensite/austenite phase changes detectable by DSC and DMTA analysis in the range of about −60 degrees Celsius (° C.) to about 120° C. in the linear elastic and/or non-super-elastic nickel-titanium alloy. The mechanical bending properties of such material may therefore be generally inert to the effect of temperature over this very broad range of temperature. In some embodiments, the mechanical bending properties of the linear elastic and/or non-super-elastic nickel-titanium alloy at ambient or room temperature are substantially the same as the mechanical properties at body temperature, for example, in that they do not display a super-elastic plateau and/or flag region. In other words, across a broad temperature range, the linear elastic and/or non-super-elastic nickel-titanium alloy maintains its linear elastic and/or non-super-elastic characteristics and/or properties.

In some embodiments, the linear elastic and/or non-super-elastic nickel-titanium alloy may be in the range of about 50 to about 60 weight percent nickel, with the remainder being essentially titanium. In some embodiments, the composition is in the range of about 54 to about 57 weight percent nickel. One example of a suitable nickel-titanium alloy is FHP-NT alloy commercially available from Furukawa Techno Material Co. of Kanagawa, Japan. Some examples of nickel titanium alloys are disclosed in U.S. Pat. Nos. 5,238,004 and 6,508,803, which are incorporated herein by reference. Other suitable materials may include ULTANIUM™ (available from Neo-Metrics) and GUM METAL™ (available from Toyota). In some other embodiments, a superelastic alloy, for example a superelastic nitinol can be used to achieve desired properties.

In at least some embodiments, portions or all of catheter shaft 20 may also be doped with, made of, or otherwise include a radiopaque material. Radiopaque materials are understood to be materials capable of producing a relatively bright image on a fluoroscopy screen or another imaging technique during a medical procedure. This relatively bright image aids the user of catheter 12 in determining its location. Some examples of radiopaque materials can include, but are not limited to, gold, platinum, palladium, tantalum, tungsten alloy, polymer material loaded with a radiopaque filler, and the like. Additionally, other radiopaque marker bands and/or coils may also be incorporated into the design of catheter 12 to achieve the same result.

In some embodiments, a degree of Magnetic Resonance Imaging (MRI) compatibility is imparted into catheter 12. For example, catheter shaft 20, or portions thereof, may be made of a material that does not substantially distort the image and create substantial artifacts (i.e., gaps in the image). Certain ferromagnetic materials, for example, may not be suitable because they may create artifacts in an MRI image. Catheter shaft 20, or portions thereof, may also be made from a material that the MRI machine can image. Some materials that exhibit these characteristics include, for example, tungsten, cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such as MP35-N® and the like), nitinol, and the like, and others.

A sheath or covering (not shown) may be disposed over portions or all of catheter shaft 20 that may define a generally smooth outer surface for catheter 12. In other embodiments, however, such a sheath or covering may be absent from a portion of all of catheter 12, such that catheter shaft 20 may form the outer surface. The sheath may be made from a polymer or other suitable material. Some examples of suitable polymers may include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, for example, DELRIN® available from DuPont), polyether block ester, polyurethane (for example, Polyurethane 85A), polypropylene (PP), polyvinylchloride (PVC), polyether-ester (for example, ARNITEL® available from DSM Engineering Plastics), ether or ester based copolymers (for example, butylene/poly(alkylene ether) phthalate and/or other polyester elastomers such as HYTREL® available from DuPont), polyamide (for example, DURETHAN® available from Bayer or CRISTAMID® available from Elf Atochem), elastomeric polyamides, block polyamide/ethers, polyether block amide (PEBA, for example available under the trade name PEBAX®), ethylene vinyl acetate copolymers (EVA), silicones, polyethylene (PE), Marlex high-density polyethylene, Marlex low-density polyethylene, linear low density polyethylene (for example REXELL®), polyester, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polytrimethylene terephthalate, polyethylene naphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI), polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), poly paraphenylene terephthalamide (for example, KEVLAR®), polysulfone, nylon, nylon-12 (such as GRILAMID® available from EMS American Grilon), perfluoro(propyl vinyl ether) (PFA), ethylene vinyl alcohol, polyolefin, polystyrene, epoxy, polyvinylidene chloride (PVdC), poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS 50A), polycarbonates, ionomers, biocompatible polymers, other suitable materials, or mixtures, combinations, copolymers thereof, polymer/metal composites, and the like. In some embodiments the sheath can be blended with a liquid crystal polymer (LCP). For example, the mixture can contain up to about 6 percent LCP.

In some embodiments, the exterior surface of the catheter 12 (including, for example, the exterior surface of catheter shaft 20) may be sandblasted, beadblasted, sodium bicarbonate-blasted, electropolished, etc. In these as well as in some other embodiments, a coating, for example a lubricious, a hydrophilic, a protective, or other type of coating may be applied over portions or all of the sheath, or in embodiments without a sheath over portion of catheter shaft 20 or other portions of catheter 12. Alternatively, the sheath may comprise a lubricious, hydrophilic, protective, or other type of coating. Hydrophobic coatings such as fluoropolymers provide a dry lubricity which improves device handling and exchanges. Lubricious coatings improve steerability and improve lesion crossing capability. Suitable lubricious polymers are well known in the art and may include silicone and the like, hydrophilic polymers such as high-density polyethylene (HDPE), polytetrafluoroethylene (PTFE), polyarylene oxides, polyvinylpyrolidones, polyvinylalcohols, hydroxy alkyl cellulosics, algins, saccharides, caprolactones, and the like, and mixtures and combinations thereof. Hydrophilic polymers may be blended among themselves or with formulated amounts of water insoluble compounds (including some polymers) to yield coatings with suitable lubricity, bonding, and solubility. Some other examples of such coatings and materials and methods used to create such coatings can be found in U.S. Pat. Nos. 6,139,510 and 5,772,609, which are incorporated herein by reference.

In addition to variations in materials, various embodiments of arrangements and configurations are also contemplated for slots 38. For example, in some embodiments, at least some, if not all of slots 38 are disposed at the same or a similar angle with respect to the longitudinal axis of catheter shaft 20. As shown, slots 38 can be disposed at an angle that is perpendicular, or substantially perpendicular, and/or can be characterized as being disposed in a plane that is normal to the longitudinal axis of catheter shaft 20. However, in other embodiments, slots 38 can be disposed at an angle that is not perpendicular, and/or can be characterized as being disposed in a plane that is not normal to the longitudinal axis of catheter shaft 20. Additionally, a group of one or more slots 38 may be disposed at different angles relative to another group of one or more slots 38. The distribution and/or configuration of slots 38 can also include, to the extent applicable, any of those disclosed in U.S. Pat. Publication No. US 2004/0181174, the entire disclosure of which is herein incorporated by reference.

Slots 38 may be provided to enhance the flexibility of catheter shaft 20 while still allowing for suitable torque transmission characteristics. Slots 38 may be formed such that one or more rings and/or tube segments interconnected by one or more segments and/or beams that are formed in catheter shaft 20, and such tube segments and beams may include portions of catheter shaft 20 that remain after slots 38 are formed in the body of catheter shaft 20. Such an interconnected structure may act to maintain a relatively high degree of torsional stiffness, while maintaining a desired level of lateral flexibility. In some embodiments, some adjacent slots 38 can be formed such that they include portions that overlap with each other about the circumference of catheter shaft 20. In other embodiments, some adjacent slots 38 can be disposed such that they do not necessarily overlap with each other, but are disposed in a pattern that provides the desired degree of lateral flexibility.

Additionally, slots 38 can be arranged along the length of, or about the circumference of, catheter shaft 20 to achieve desired properties. For example, adjacent slots 38, or groups of slots 38, can be arranged in a symmetrical pattern, such as being disposed essentially equally on opposite sides about the circumference of catheter shaft 20, or can be rotated by an angle relative to each other about the axis of catheter shaft 20. Additionally, adjacent slots 38, or groups of slots 38, may be equally spaced along the length of catheter shaft 20, or can be arranged in an increasing or decreasing density pattern, or can be arranged in a non-symmetric or irregular pattern. Other characteristics, such as slot size, slot shape, and/or slot angle with respect to the longitudinal axis of catheter shaft 20, can also be varied along the length of catheter shaft 20 in order to vary the flexibility or other properties. In other embodiments, moreover, it is contemplated that the portions of the tubular member, such as a proximal section, or a distal section, or the entire catheter shaft 20, may not include any such slots 38.

As suggested herein, slots 38 may be formed in groups of two, three, four, five, or more slots 38, which may be located at substantially the same location along the axis of catheter shaft 20. Alternatively, a single slot 30 may be disposed at some or all of these locations. Within the groups of slots 38, there may be included slots 38 that are equal in size (i.e., span the same circumferential distance around catheter shaft 20). In some of these as well as other embodiments, at least some slots 38 in a group are unequal in size (i.e., span a different circumferential distance around catheter shaft 20). Longitudinally adjacent groups of slots 38 may have the same or different configurations. For example, some embodiments of catheter shaft 20 include slots 38 that are equal in size in a first group and then unequally sized in an adjacent group. It can be appreciated that in groups that have two slots 38 that are equal in size and are symmetrically disposed around the tube circumference, the centroid of the pair of beams (i.e., the portion of catheter shaft 20 remaining after slots 38 are formed therein) is coincident with the central axis of catheter shaft 20. Conversely, in groups that have two slots 38 that are unequal in size and whose centroids are directly opposed on the tube circumference, the centroid of the pair of beams can be offset from the central axis of catheter shaft 20. Some embodiments of catheter shaft 20 include only slot groups with centroids that are coincident with the central axis of the catheter shaft 20, only slot groups with centroids that are offset from the central axis of catheter shaft 20, or slot groups with centroids that are coincident with the central axis of catheter shaft 20 in a first group and offset from the central axis of catheter shaft 20 in another group. The amount of offset may vary depending on the depth (or length) of slots 38 and can include other suitable distances.

Slots 38 can be formed by methods such as micro-machining, saw-cutting (e.g., using a diamond grit embedded semiconductor dicing blade), electron discharge machining, grinding, milling, casting, molding, chemically etching or treating, or other known methods, and the like. In some such embodiments, the structure of the catheter shaft 20 is formed by cutting and/or removing portions of the tube to form slots 38. Some example embodiments of appropriate micromachining methods and other cutting methods, and structures for tubular members including slots and medical devices including tubular members are disclosed in U.S. Pat. Publication Nos. 2003/0069522 and 2004/0181174-A2; and U.S. Pat. Nos. 6,766,720; and 6,579,246, the entire disclosures of which are herein incorporated by reference. Some example embodiments of etching processes are described in U.S. Pat. No. 5,106,455, the entire disclosure of which is herein incorporated by reference. It should be noted that the methods for manufacturing catheter 12 may include forming slots 38 in catheter shaft 20 using these or other manufacturing steps.

In at least some embodiments, slots 38 may be formed in tubular member using a laser cutting process. The laser cutting process may include a suitable laser and/or laser cutting apparatus. For example, the laser cutting process may utilize a fiber laser. Utilizing processes like laser cutting may be desirable for a number of reasons. For example, laser cutting processes may allow catheter shaft 20 to be cut into a number of different cutting patterns in a precisely controlled manner. This may include variations in the slot width, ring width, beam height and/or width, etc. Furthermore, changes to the cutting pattern can be made without the need to replace the cutting instrument (e.g., blade). This may also allow smaller tubes (e.g., having a smaller outer diameter) to be used to form catheter shaft 20 without being limited by a minimum cutting blade size. Consequently, catheter shafts 20 may be fabricated for use in neurological devices or other devices where a relatively small size may be desired.

It should be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of steps without exceeding the scope of the invention. This may include, to the extent that it is appropriate, the use of any of the features of one example embodiment being used in other embodiments. The invention's scope is, of course, defined in the language in which the appended claims are expressed. 

What is claimed is:
 1. A renal nerve modulation catheter, comprising: an elongate catheter shaft; wherein the elongate catheter shaft has a plurality of cuts formed therein that define a plurality of electrode assemblies; wherein each of the plurality of electrode assemblies includes a main strut that branches into one or more branched spacer struts extending from the main strut and extending radially outward when in an expanded configuration, the main strut including flanking strut regions on either side of an electrode extending from the main strut and disposed between the flanking strut regions, the electrode extending radially inward in a direction opposite from the one or more branched spacer struts.
 2. The renal nerve modulation catheter of claim 1, wherein the plurality of electrode assemblies includes three or more electrode assemblies.
 3. The renal nerve modulation catheter of claim 1, wherein the plurality of electrode assemblies includes four or more electrode assemblies.
 4. The renal nerve modulation catheter of claim 1, wherein the plurality of electrode assemblies includes five or more electrode assemblies.
 5. The renal nerve modulation catheter of claim 1, wherein at least some of the plurality of electrode assemblies are longitudinally-spaced from one another.
 6. The renal nerve modulation catheter of claim 1, wherein the plurality of electrode assemblies form a circumferential array.
 7. The renal nerve modulation catheter of claim 1, wherein includes a distal region having a plurality of slots formed therein.
 8. The renal nerve modulation catheter of claim 1, wherein includes a proximal region having a plurality of slots formed therein.
 9. A renal nerve modulation catheter, comprising: an elongate tubular member having an electrode array portion; wherein the electrode array portion has a plurality of cuts formed therein that define a plurality of longitudinally-spaced electrode assemblies; and wherein the each of the plurality of longitudinally-spaced electrode assemblies includes a main strut that branches into one or more branched spacer struts extending from the main strut and extending radially outward when in an expanded configuration, the main strut including flanking strut regions on either side of an electrode extending from the main strut and disposed between the flanking strut regions, the electrode extending radially inward in a direction opposite from the one or more branched spacer struts.
 10. The renal nerve modulation catheter of claim 9, wherein includes a distal region having a plurality of slots formed therein, a proximal region having a plurality of slots formed therein, or both. 